Gold nanocomposites

V. Subraniam, E. Wolf, P.V. Kamat, Catalysis with Ti02/gold nanocomposites. Effect of metal particle size on the Fermi level equilibration, J. Am. Chem. Soc. 126 (2004) 4943-4950. 

Arabinogalactan is transparent both in UV and visible ranges, and electronic absorption spectroscopy can be successfully used to study arabinogalactan assisted nanoparticles. The absorption spectra of the silver and gold nanocomposites solutions have intensive absorption peaks at 420 and 524 nm, respectively (Fig. la), which proves the presence of silver and gold zero-valence metals [3]. The peaks are attributed to collective excitations of conduction electrons (plasmonic resonance). This fact is of interest for synthesis of water soluble highly efficient non-linear optical materials [1]. 

The XRD patterns (WAXS) of the gold nanocomposites formed at the presence of different surface-active materials compared with those of the initial clay are given in Fig. 1 (right). For all composites the highest peak intensities are at 20= 38.2° corresponding to Au (111). Other smaller peaks are observed at 20= 44.4°, 64.8° and 77.9° corresponding to the (200), (220) and (311) planes. All peaks are related to the cubic phase of Au. 

Kulak A et al (2003) Controlled assembly of nanoparticle-containing gold and silica microspheres and silica/gold nanocomposite spheroids with complex form. Chem Mater 15(2) 528-535... 

The poly (vinyl alcohol)-gold nanocomposites were finally drawn at 120°C up to a draw ratio (DR), defined as the ratio of the length before and after drawing, of 5. It is well known that the polymer molecules orient upon drawing, and it was evident from TEM images of thin sections of the drawn materials... 

Figure 9.4. UV-Vis spectra of a drawn poly(vinyl alcohol)-gold nanocomposite in polarized light at different angles cp representing the angle between the polarization plane of the light and the drawing direction of the nanocomposite. The angle cp varies from 0° to 90° in steps of 10°, and a pure poly(vinyl alcohol) sample with similar thickness as the nanocomposite was inserted in the reference beam of the spectrometer.

TABLE 9.1. Absorption Maxima of Drawn Poly(ethylene)-Gold Nanocomposites (Draw Ratio 15) at Different Reaction Conditions and Different Angles (p Between the Polarization Plane of the Incident Linearly Polarized Light and the Drawing Axis of the Specimen"... 

Figure 9.6. Scanning electron micrograph (detection of backscattered electrons) of a poly(ethylene)-gold nanocomposite. The bright lines represent arrays of gold nanoparticles that are not resolved individually.

S. K. Pillalamarri, F.D. Blum, and M.F. Bertino, Synthesis of polyaniline-gold nanocomposites using grafting from approach, Chem. Commun., 4584-4585 (2005). 

J.A. Smith, M. Josowicz, and J. Janata, Polyaniline-gold nanocomposite system, J. Electrochem. Soc., 150, E38A-E388 (2003). 

P. R. B. Oiiveira Marques, A. Lermo, S. Campoy, H. Yamanaka, J. Barb6, S. Aiegret, and M. I. Pividori, Doubie-tagging poiymerase chain reaction with a thiolated primer and eiectrochemicai genosensing based on gold nanocomposite sensor for food safety. Ana/. Chem., 81, 1332-1339 [2009],... 

A similar immobilization methodology has been used to develop a DNA-sensing platform for Helicobacter pylori [13]. Rigid conducting gold nanocomposites have been also modified with this strategy. 

Ruiyi, L., Qianfang, X., Zaijun, L., Xiulan, S., and Junkang, L. [2013]. Electrochemical immunosensor for ultrasensitive detection of microcystin-LR based on giaphene-gold nanocomposite/fiinctional conducting polymer/gold nanoparticle/ionic liquid composite film with electrodeposition. Biosens. Bioelectron., 44, pp. 235-240. 

Nanocomposite particles. A few examples of photoresponsive silica and gold nanocomposite particles are given here. Both photo-isomerizable and photocleavable units were graphted on the surface of the particles to achieve photocontrollable functions. 

Subramanian, V., Wolf, E. E., Kamat, P. (2004). Catalysis with Ti02/gold nanocomposites effect of metal particle size on the fermi level equilibration. Journal of the American Chemical Society, 126, 4943-4950. http //dx.doi.org/10.1021/ja0315199. 

Chemically bonded scaffolds are superior to physically adsorbed scaffolds in terms of the robustness of the resulting gold nanocomposites. Although most polymers introduced by the grafting from method are artificial polymers [80, 81], representative biopolymers such as oligonucleotides and peptides can also be introduced. 

Conjugation of as-prepared GNPs with as-prepared polymers is the most common and simplest method for preparing gold nanocomposites because mixing of the as-prepared materials can eliminate uncertainty factors such as the dispersion of GNP size and molecular weight. 

Figure 6.5. (a) TEM of crystalline gold colloid particles (the halo of organic molecules is invisible), (b) computer simulation of a dendrimer nanocomposite, (c) HRTEM of a gold nanocomposite particle containing 14 Au atoms. (D) Dendrimer template. CNDs are in the middle of the structural "spectrum", to the far left lie dendrimer compatibilized "hard" gold nanoparticles, and "soft" dendrimers are on the right. 

Figure 6.7. Dendrimer/gold nanocomposites enable construction of uniform nanop>articles with different diameters and surface charges (left and right is negative charge, + is positive charge, and N is neutral) to be produced that are otherwise identical. Recent experiments show that the size and charge of the nanoparticles influence their hiodistrihu-tion in mice (figure drawn not to scale)...

Silva JN, Bezerra MC, Ftuias PMA. Novel and simple route for the synthesis of core-sheU chitosan-gold nanocomposites. Mater Chem Phys. 2012 135(l) 63-7. 

Lin, Y-L, Jen, J-C, Hsu, S-h, and Chiu, I-M. 2008. Sciatic nerve repair by microgrooved nerve conduits made of cliitosan-gold nanocomposites. Surg Neurol 70(Suppl 1) S9-S18. 

Metal nanopartides can also be cited. The characteristic properties of metal nanopartides and nanocomposites have been the subject of study because of their unique optical properties. Combining metal and polymer together enhances the optical properties of nanometals. Srivastava et al. 3] studied the optical properties of gold nanocomposites by changing the size and fraction of gold nanopartides. The optical properties of nanocomposite films of various thicknesses with different sizes and volume fraction of gold nanopartides have been studied using spectroscopic... 

---